Field of the Invention
The present invention relates generally to image processing, and more particularly it relates to a technology for searching corresponding image regions between images having different blurred states.
Description of the Related Art
In image processing, methods have been known which use two or more images captured under different photographing conditions to acquire a distance to a subject (hereinafter, called a subject distance) and may use the acquired subject distance to generate a new image as if it has been captured under a different condition from conditions under which the images have been actually captured. Block matching is a typical one of those methods and may search corresponding points being corresponding pixels between two or more images acquired by photographing a same subject from different points of view to acquire a parallax between the images. The parallax between images acquired by block matching and positional information on positions of points of view where the images are photographed if known may be used to acquire a distance to the subject by using simple trigonometry. An improved method of such block matching has been proposed, for example, by Japanese Patent Application Laid-Open No. 2009-293970. In this improved block matching method, image processing adaptively changes a block size of search blocks for searching corresponding points in accordance with whether the search block includes edge areas of the image or not for higher accuracy of search for corresponding points.
The method disclosed in Japanese Patent Application Laid-Open No. 2009-293970, however, may possibly lower the accuracy of search for corresponding points between images captured at different point-of-view positions and having different blurred states (in-focus states) due to a difference in focal length, f-number or focused position if any. The term “blurred state” here refers to a parameter for determining a blur (deviation) of an image with respect to an in-focus position or a depth of field.